Intravascular filters are typically used in combination with other thrombolytic agents to treat pulmonary embolism occurring within a patient. Such devices are generally implanted within a vessel such as the inferior or superior vena cava, and function by capturing blood clots (emboli) contained in the blood stream before they can reach the lungs and cause permanent damage to the body. To trap emboli contained within the blood, many conventional filters include an apical head operatively coupled to a plurality of elongated filter legs that can be expanded within the body to form a conical-shaped surface that captures blood clots without disturbing the flow of blood. Once collected, a natural clot lysing process occurs within the body to dissolve the blood clots collected by the filter.
Delivery of the intravascular filter within the body is generally accomplished via an introducer sheath percutaneously inserted through the femoral (groin) or jugular (neck) veins. Such introducer sheaths are typically tubular in shape, and include an interior lumen configured to transport the filter in a collapsed position through the body. Once transported to a desired location in the body, the filter can then be removed from within the introducer sheath, allowing the filter legs to spring open and engage the vessel wall. A needle, hook, barb, prong, wedge or other attachment means disposed on the free end of each filter leg can be used to secure the filter to the vessel wall.
The efficacy of the intravascular filter to capture blood clots is dependent in part on the ability of the filter to center when deployed within the blood vessel. Tilting of the filter may result if the apical head is not aligned centrally within the vessel, causing the filter legs to asymmetrically engage the vessel wall. Tilting of the filter may also result if the introducer sheath used to deploy the filter is off-centered within the blood vessel. In certain circumstances, tilting of the filter may affect the ability of the device to efficiently capture blood clots contained in the blood.